Text messages are used to interact with automated systems to provide information (e.g., news and special offers) to receivers and to engage them with certain activities (e.g., voting and surveys). Using text messages, service providers can notify mobile phone users about promotions, payment due dates and other notifications that were sent by a post, e-mail or voicemail. For example, advertisers may use text messages to promote a business, product, and/or service. However, under conventional technologies, advertisers have problems evaluating whether their text messages are effective with respect to certain users and whether there is a need to send additional text messages to these users.